1. Field
One or more embodiments relate to apparatuses and methods of determining roll postures of projectiles.
2. Description of the Related Art
All around the world, research has been actively conducted to improve the firepower of shells and munitions. In addition to research for increasing the amount of gunpowder or improving the power of gunpowder to improve the firepower of shells and munitions, research for improving the accuracy of shells and munitions to concentrate firepower has been actively conducted.
An example thereof may be a trajectory correctable munition with a guidance and control function on a shell. As for general shells and munitions, as range increases, accuracy may decrease and dispersion may increase. In order to overcome this limitation, trajectory correctable munitions are being globally developed to increase power by allowing a maximum approach to targets by adding a guidance and control function to shells. A general munition may roll-spin at high speed for flight stability. When a shell uses a tail wing to secure flight stability, the shell may not roll-spin; however, a shell without a tail wing may secure flight stability through a roll-spin. Thus, roll-spinning shells and munitions may need to estimate roll postures for guidance and control. In the case of a guided missile, a roll posture may be measured or estimated through an inertial navigation system; however, in the case of a spin-stabilized munition, due to complex motion during flight, it may be difficult to use an inertial navigation system. As an alternative, research is being conducted into a method of estimating a roll posture by using the strength of received power or by using the phase of a signal received through a global positioning system (GPS). However, the GPS may be disabled by jamming, and the system may be complicated due to the computational complexity of the method described above. As another alternative, research is being conducted into a method of estimating the posture of a shell or munition by measuring a geomagnetic field. For example, in order to increase the power of an air-burst munition, research is being conducted to concentrate the firepower on the ground by detecting the ground. Since the GPS-based system described above is too large to be applied to small munitions, a method based on geomagnetism is being researched instead. However, since geomagnetism changes depending on launch positions, a value of geomagnetism at a launch position may have to be previously inserted into a munition to detect an accurate ground side.